261640917 has 12 divisors (see below), whose sum is σ = 380246464. Its totient is φ = 173356200.

The previous prime is 261640889. The next prime is 261640921. The reversal of 261640917 is 719046162.

261640917 is a `hidden beast` number, since 2 + 6 + 1 + 640 + 9 + 1 + 7 = 666.

It is not a de Polignac number, because 261640917 - 2⁷ = 261640789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261640937) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 87709 + ... + 90642.

Almost surely, 2^261640917 is an apocalyptic number.

It is an amenable number.

261640917 is a deficient number, since it is larger than the sum of its proper divisors (118605547).

261640917 is a wasteful number, since it uses less digits than its factorization.

261640917 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178520 (or 178517 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 261640917 is about 16175.3181421572. The cubic root of 261640917 is about 639.5903278261.

The spelling of 261640917 in words is "two hundred sixty-one million, six hundred forty thousand, nine hundred seventeen".